Method for filling a plastic container

Abstract

A method for filling a plastics container, wherein an excess pressure is built up in the filled and closed container. The method includes the following method steps: filling the plastics container with a liquid, and closing the filled plastics container. In a deformation step, the container, prior to being closed, is deformed by a mechanical force such that the cross-sectional shape of the container is changed and its volume is thereby increased. In a pressure relief step, the mechanical force is removed once the container has been closed, as a result of which the volume contraction causes an excess pressure to build up in the container, and the filling height of the liquid increases.

Claims

1. A method for filling a plastics container, comprising the following method steps: filling the plastics container with a liquid, and closing the filled plastics container, wherein in a deformation step, the container, prior to being closed, is deformed by a mechanical force such that the cross-sectional shape of the container is changed and its volume is thereby increased and in a pressure relief step, the mechanical force is removed once the container has been closed, as a result of which the volume contraction causes an excess pressure to build up in the container, and the filling height of the liquid to rise.

2. The method according to claim 1, wherein the cross-section of the container has a smallest diameter and in the deformation step the smallest diameter is increased.

3. The method according to claim 1, wherein the mechanical force is a compressive force and acts on the container in such a way that the smallest diameter increases.

4. The method according to claim 1, wherein the mechanical force is a tensile force and acts on the container in such a way that the smallest diameter increases.

5. The method according to claim 1, wherein the container has an oval cross-section with a main axis with a largest diameter and a minor axis with a smallest diameter, and the mechanical force acts on the main axis as a compressive force or on the minor axis as a tensile force.

6. The method according to claim 1, wherein the cross-section of the container is given a substantially circular shape in the deformation step.

7. The method according to claim 1, wherein the deformation step is carried out before filling the container.

8. The method according to claim 1, wherein the pressure relief step is realized by expansion of decorative elements attached to the container surface.

Description

(1) Further advantages and features will become apparent from the following description of an embodiment of the invention with reference to the schematic drawings. In the figures, in a representation that is not to scale:

(2) FIG. 1: shows the cross-section of an oval bottle before a deformation step;

(3) FIG. 2: shows the cross-section of the bottle during the deformation step;

(4) FIG. 3: shows the cross-section of the bottle after a pressure relief step;

(5) FIG. 4: is a side view of the bottle before the deformation step;

(6) FIG. 5: is a side view of the bottle during the deformation step;

(7) FIG. 6: is a side view of the bottle after the pressure relief step, and

(8) FIGS. 7a, 7b and 7c: are three views for calculating the surface area or volume of a bottle filled according to the method according to the invention.

(9) FIGS. 1 to 4 are a cross-section and a side view of a container, and in particular a bottle. The container or bottle is designated as a whole with the reference sign 11. The bottle preferably has an oval or elliptical cross-section, as this shape is ideal for deforming the bottle. Before the bottle is filled, it is mechanically deformed so that the bottle is brought into an approximately circular shape. If the bottle 11 is filled and closed and then mechanically relieved of pressure again, the filling height increases as a result of the volume reduction, and an increased internal pressure builds up. The principle of elastic deformation is used here, in order that the bottle 11 obtains a larger volume during the filling process and an internal pressure can subsequently build up in the bottle.

(10) The oval cross-section has a main axis 13 with a largest diameter and a minor axis 15 with a smallest diameter. By a mechanical force, the bottle 11 is compressed on the main axis 13 or pulled apart on the minor axis 15. This gives the bottle 11 the cross-section shown in FIG. 2. The force can be applied as a compressive force, for example via two opposing sliders, and can act on the main axis 13. The force can also act as a tensile force, for example via two opposing suction cups which act on the minor axis 15.

(11) After the deformation step, the cross-section has a shape that is as circular as possible, in which the volume of the bottle is significantly increased. A liquid 12 is filled into the deformed bottle 11 with the increased volume. After the bottle is closed, the force is removed in a pressure relief step. The bottle tries to return to its original cross-sectional shape. In doing so, it compresses the liquid 12 and the air 14 in the closed headspace, whereby an internal pressure builds up and the filling height 16 of the liquid 12 rises. This makes the bottle 11 mechanically more stable. The pressure-relieved cross-sectional shape of the filled bottle is shown in FIG. 3. Due to this effect, it is possible to make bottles lighter in weight because the mechanical stability is no longer determined solely by the material or the wall thickness of the bottle. The material saving potential is between 10 and 20%. In addition, the increased volume also creates an increased headspace. This increased headspace can be used during filling to absorb foam generated during filling, to compensate for the volume of the filling lance immersed in the container, or to prevent liquid from spilling over. Due to the pressure relief or the resulting internal pressure, the liquid 12 is pushed upwards and partially fills the headspace. This gives the bottle a filling level that is perceived as positive by the consumer. The excess pressure makes the bottle firmer to grip and more stable for transport. Just as in the case of nitrogen-based technology, the weight of the bottle can be reduced.

(12) FIGS. 7a to 7c are part of an illustrative example: FIGS. 7a, 7b and 7c show three cross-sections with identical circumferences (U=31.4 cm) but different surface areas. The surface areas were calculated using the formula for calculating the surface area of an ellipse. In order to calculate the volume, a bottle height of 10 cm was assumed. FIG. 7a corresponds to the initial cross-section of the bottle 11 before the deformation step. The main axis a has a length of 15 cm and the minor axis b has a length of 2.9 cm. The surface area is 33.9 cm.sup.2 and the volume is 339 ml.

(13) If the cross-section is deformed to a circle with a radius of 5 cm, the surface area changes to 78.5 cm.sup.2 and the volume is 785 ml. The volume increases by 446 ml due to the deformation. After pressure relief, the cross-section is 53.7 cm.sup.2 and the volume is reduced to 537 ml. This reduces the volume by 248 ml, which can serve to create an excess pressure and raise the filling level.

(14) This illustrative example shows how great the potential is to generate large volume differences and thus excess pressures through resilient volume contraction. As a rule, even a small deformation is sufficient to achieve the desired excess pressure.

LIST OF REFERENCE SIGNS

(15) 11 container, bottle 12 liquid 13 main axis, largest diameter 14 air 15 minor axis, smallest diameter of the container 16 filling height